1. Field of the Invention
The present invention relates to an internetworking system and method, and more particularly to an internetworking system and method for interconnecting a plurality of networks that use different protocols.
2. Description of the Related Art
Today""s network systems have increased in size and complexity to serve the diverse user needs for telecommunications services. The proliferation of multi-protocol routers, gateways, and other like devices has become a driving force for interworking between local networks, as opposed to isolated networks in the past. This also promotes the rapid development of heterogeneous network environments where dissimilar protocols are used together. In order to monitor and control such a sophisticated environment, many of conventional network management systems deploy a dedicated network management station (NMS) for each individual network. In recent years, however, there is an increasing demand for more efficient network management systems which can supervise network elements (NEs) deployed over different networks in. a centralized manner.
The Japanese Unexamined Patent Application Publication No. 10-327152 (1998) is one example of conventional network management techniques. According to this publication, a network management system employs all kinds of necessary protocol stacks, thereby supervising the entire network environment using different protocols.
FIG. 50 shows a conventional network management system. In this system, an NMS 500 is coupled to a network A, and NEs 301 and 302 are located on another network B, where the two networks A and B use different communication protocols. A gateway network element (GNE) 600 is interposed between the networks A and B to provide network mediation services to control internetworking processes between them.
To illustrate how the network B is managed, it is assumed here that the NMS 500 now intends to access the remote NE 301. Having a lower-layer protocol stack of the network B being monitored, the NMS 500 produces a header that complies with the protocol specifications used in the network B. Since the network A, on the other hand, has its own frame format, the NMS 500 inserts the above header to the data field of a frame for the network A to which the NMS 500 belongs to. In this way, the NMS 500 creates a hybrid frame containing information about both protocols. After setting up a connection C10 to reach the NE 301 via the GNE 600, the NMS 500 sends out the hybrid frame.
The above-described technique enables the NMS 500 to have an end-to-end access to the NE 301 located on the network B, whose protocol is different from the network A""s. The NMS 500 can communicate with the other remote NE 302 in a similar way. That is, the NMS 500 asks the GNE 600 to establish a connection C20 extending to the NE 302, creates a like hybrid frame, and sends it toward the NE 302.
Such conventional internetworking techniques, however, have the following disadvantages. First, it requires the NMS 500 to set up a dedicated connection to every destination NE, which produces a number of connections at a time. This naturally causes increased traffic and consequent slow access to a plurality of NEs.
Second, in the conventional internetworking system, the NMS 500 has to create a hybrid frame containing information about both protocols used in the networks A and B, when transporting data in this heterogeneous environment. Such a construct of hybrid frames may result in a large amount of data to be transmitted over the networks, thus causing a substantial increase in the network traffic.
Third, the conventional internetworking system is quite limited in its service coverage area. Actually, the NMS 500 only covers its local network A and its neighboring network B, which is immediately adjacent to the network A. FIG. 51 shows another conventional system which consists of three networks A, B, and D whose protocols are different from one another. The network D is linked with the network B via a GNE 601, and an NE 303 is located on this network D. In such a conventional system, the NMS 500 is unable to monitor the network D, because it is not directly linked with the network A, where the NMS 500 resides. The problem is that the NMS 500 cannot resolve the address of the NE 303 on the network D, since the network D and its neighboring network B do not share their address resolution protocols. For this reason, the NMS 500 cannot communicate with the NE 303.
Taking the above into consideration, an object of the present invention is to provide an internetworking system which efficiently interconnects heterogeneous networks by mediating between different protocols.
Another object of the present invention is to provide an internetworking method which efficiently interconnects heterogeneous networks by mediating between different protocols.
To accomplish the first object note above, according to the present invention, there is provided an internetworking system for interconnecting a plurality of networks that use different protocols. This internetworking system comprises a network management station and a mediation device. The network management station comprises the following elements:
a first connection setting unit which establishes a first connection over a first network in a point-to-point fashion;
a downstream frame generator which produces a downstream frame containing an identifier of a network element that the network management station intends to interact with, wherein the network element being on a second network whose communication protocol is different from that of the first network; and
a frame communication unit which sends out the downstream frame through the first connection, and/or processes an upstream frame received through the first connection.
The mediation device, on the other hand, comprises the following elements:
a second connection setting unit which establishes a second connection in a point-to-point or point-to-multipoint fashion over the second network to reach the network element; and
a frame mediation unit which receives the downstream frame through the first connection and forwards the received downstream frame to the network element through the second connection, or receives an upstream frame from the network element through the second connection and forwards the received upstream frame to the network management station through the first connection.
Further, to accomplish the second object note above, the present invention provides an internetworking method for interconnecting heterogeneous network environments that use different protocols. This internetworking method comprises the following steps:
(a) establishing a first connection over a first network in a point-to-point fashion;
(b) producing a downstream frame containing an identifier of a network element that is to be reached, the network element being on a second network whose communication protocol is different from that of the first network;
(c) sending out the downstream frame through the first connection, or processing an upstream frame received through the first connection;
(d) establishing a second connection in a point-to-point or point-to-multipoint fashion over the second network to reach the network element; and
(e) receiving the downstream frame through the first connection and forwarding the received downstream frame to the network element through the second connection, or receiving an upstream frame from the network element through the second connection and forwarding the received upstream frame through the first connection.
The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.